This thesis discusses techniques for improving the fault tolerance of multithreaded applications. We consider the impact on fault tolerance methods of sharing address space and resources. We develop techniques in two broad categories: conservative multithreaded fault-tolerance (C-MTFT), which recovers an entire application on the failure of a single thread, and optimistic multithreaded fault-tolerance (OMTFT), which recovers threads independently as necessary. In the latter category, we provide a novel approach to recover hung threads while improving recovery time by managing access to shared resources so that hung threads can be restarted while other threads continue execution. / text

published_or_final_version / abstract / toc / Electrical and Electronic Engineering / Master / Master of Philosophy

published_or_final_version / Computer Science / Master / Master of Philosophy

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System-level diagnosis is considered to be a viable alternative to circuit-level testing in complex multiprocessor systems. The characterization problem, the diagnosability problem, and the diagnosis problem in this framework have been widely studied in the literature with respect to a special fault class, called t-fault class, in which all fault sets of size up to t are considered. Various models for the interpretation of test outcomes have been proposed and analyzed. Among these, four most known models are: symmetric invalidation model, asymmetric invalidation model, symmetric invalidation model with intermittent faults, and asymmetric invalidation model with intermittent faults. / In this thesis, a completely new generalization of the characterization problem in system-level diagnosis area is developed. This generalized characterization theorem provides necessary and sufficient conditions for any fault-pattern of any size to be uniquely diagnosable under all the four models. Moreover, the following three results are obtained for the t-fault class: (1) the characterization theorem for t-diagnosable systems under the asymmetric invalidation model with intermittent faults is developed for the first time; (2) a unified t-characterization theorem covering all the four models is presented; and finally (3) it is proven that the classical t-characterization theorems under the first three models and the new result for the fourth model, as mentioned in (1) above, are special cases of the generalized characterization theorem. / The general diagnosability problem is also studied. It is shown that the single fault diagnosability problem, under the asymmetric invalidation model is Co-NP-complete. / As regards the diagnosis problem, most of the diagnosis algorithms developed thus far are global algorithms in which a complete syndrome is analyzed by a single supervisory processor. In this thesis, distributed diagnosis algorithms for regular interconnected structures are developed which take advantage of the interconnection architecture of a multiprocessor system.

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